Investigating the composition of periodic nano-size column structures of anodic titanium oxide by the method of IR spectroscopy

Periodic column structures of anodic tantalum oxide (ATO), formed by anodizing in different regimes a Ta—Al two-layer thin-film composition in an oxalic-acid solution as well as the films of dense anodic oxide and thermal tantalum oxide, are investigated by the methods of scanning electron microscopy and reflection IR spectroscopy. It is established that the ATO nano-size columns are composed of at least three known oxide phases from a Ta—O system: TaO, TaO₂ and Ta₂O₅. The structure of tantalum oxide compounds is amorphous with the near order (inclusions) of TaO₂ rutile, rhombic Ta₂O₅, and α- and β-modifications of tantalum pentoxide. The dense-ATO films are distinguished by a more disordered structure of the oxygen compounds of tantalum and an increased content of amorphous tantalum pentoxide. The thermal-ATO films have the most ordered structure of all the oxide phases that enter in their composition and increased relative contents of α- and β-Ta₂O₃. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 850–856, November–December, 1998.